The indoor soil cultivation and corn seedlings pot experiment were conducted to research ammonia volatilization and the effect of modified urea on soil inorganic nitrogen and pH.The results showed that:(1) ammonia volatilization of modified urea significantly reduced compared to that of common urea,thereby reducing the loss of nitrogen; within a certain range,the greater soil moisture,the lower ammonia volatilization.(2) Nitrification inhibitor dicyandiamide （DCD） could inhibit soil nitrification,which prolonged the duration of NH+4 N in soil,thus reducing the loss of NO-3 N; and within a certain range,the higher concentration of DCD,the better effect of suppressing.(3) Soil pH had a very significant index positive correlation with NH+4 N,a very significant negative linear correlation with NO-3 N,and a very significant polynomial correlation with soil inorganic nitrogen.Therefore,the modified urea could significantly reduce NH3 volatilization and inhibit soil nitrification to lower nitrogen losses.